Brake master cylinder cup seal with valve

ABSTRACT

A brake master cylinder assembly having a piston cup seal equipped with a valve. The cup seal valve allows the rapid resupply of pressure fluid from the supply reservoir to the highpressure chamber of the master cylinder at such times when there is little or no pressure in such chamber. The valve provides an unobstructed fluid flow passageway through the cup seal to the high-pressure chamber during bleeding of the brake system equipped with the master cylinder and permits the reservoir to supply replenishment fluid to the high-pressure chamber upon a retraction stroke of the piston.

United States Patent 11 1 Sindelar et al.

1451 Apr.2, 1974 [54] BRAKE MASTER CYLINDER CUP SEAL 2,872,705 2/1959Labarrc 417/511 WITH VALVE 2,192,012 2/1940 La Bric....

' 1,889,987 l2/l932 H1.:idlof'i'.. 60/588 [75] Inventors: Ernest C.Sindelar,.Aurora; Duane 5mm, Oswcgo, both of Primary Examiner Edgar W.Geoghegan [73] Assignce: Caterpillar Tractor C0., Peoria, lll. AssistantExamme A- Zupclc Attorney, Agent, or Firm-1Fryer, Tjensvold, Phillips &[22] F1led: Sept. 12, 1972 Lempio [2]] Appl. No.: 288,402

[57] ABSTRACT [52] U S Cl 60/588 60/589 7/511 A brake master cylinderassembly having a piston cup [51] Flsb 7/08 seal equipped with a valve.The cup seal valve allows [58] Fie'ld 41761 the rapid resupply ofpressure fluid from the supply I 92/24 1 reservoir to the high-pressurechamber of the master cylinder at such times when there is little or nopres- [56] References Cited sure in such chamber. The valve provides anunobstructed fluid flow passageway through the cup seal to UNITED STATESPATENTS the high-pressure chamber during bleeding of the 2,847,8278/1958 Johnson, 417/511 brake system equipped with the master cylinderand 31141303 7/1964 Baldwin permits the reservoir to supplyreplenishment fluid to the high-pressure chamber upon a retractionstroke of agner..... 2,136,835 11/1938 Bcgg the plston' v 3,318,2565/1967 Green 417/511 10 Claims, 7 Drawing Figures a Q 32 21 2 a /61 u ar45 712 l I 1 MW M W A I .59 Q8 NM '111111 E 38- 35 2g 2g o O -7 20 28 IA PAIENIEBAPR 2:914 (1800.541

sum 2 er 3 2 21 H: WWMH F V W/g/I M/ PAIENIEBAPR 21m 3.800 541 sumaorsBRAKE MASTER CYLINDER CUP SEAL WITH VALVE BACKGROUND OF THE INVENTIONthe cup seal and the outlet end of the master cylinder.

At times, such as when brake system is bled, there will be little or nopressure in the high-pressure chamber of the brake master cylinder.Under these lowpressure conditions, desired separation'of the cup sealfrom the piston face will be sluggish and the brake pedal will have tobe stroked several times to permit the reservoir to replenish depletedfluid in the highpressure chamber. Bleeding under such a procedure istime-consuming and generally requires two persons.

SUMMARY AND OBJECTS OF THE INVENTION The present invention provides amaster cylinder cup seal which solves the above-mentioned problem andwhich is equipped with a valve capable of providing an unobstructedfree-flow path from the reservoir to the high-pressure chamber of themaster cylinder at any time the master piston assembly is static. Theinvention, while providing free flow between the reservoir and thehigh-pressure chamber whenever the piston assembly is static, alsoinsures a complete seal between the piston, the cup seal, and thecylinder bore whenever the piston assembly is stroked in a pumpingdirection. i y

An object of the present invention is to provide a piston. cup sealhaving a passageway therethrough provided with a valve which passagewayis held normally open by said valve but which is securely closed whenthe piston is actuated on a pumping stroke.

Other objects and advantages of the present invention will becomeapparent upon reference to the accompanying drawings and followingdescription.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectionalelevation taken generally through the center ofa master cylinderassembly showing the preferred embodiment of the present invention withthe components thereof disposed in a piston-actuated position;

FIG. 2 is a fragmentary section of the master cylinder assembly of FIG.1 but showing the components of the or conduits which lead to theindividual wheel cylinders showing the components of the assembly in apistonactuated position;

FIG. 5 is a view similar to FIG. 2 but showing the cup seal valveillustrated in FIG. 4;

FIG. 6 is a view similar to FIG. 2 but showing another alternateconstruction for the piston seal valve of the present invention; and

FIG. 7 is an isometric view of the seal valve illustrated in FIG. 6.

DETAILED DESCRIPTION With reference to FIGS. 1 and 2 in the drawings, acomplete brake master cylinder assembly is shown generally at 10. Suchassembly includes a body 11 having a fluid supply reservoir 12 with afiller cap 13. Body part 11 has a bore 14 with an open end 17 and valvedoutlet end 18. The outlet end 18 communicates with a reduced diameterbore 19 which, in turn, communicates with a threaded coupling bore 20.The threaded bore 20 is adapted for connection to a plurality of lines(not shown) for the .vehicle. in which the present system is utilized. Amake-up port 21 provides communication between the bore 14 and thereservoir 12. An axiallyspaced metering orifice bypass port 24 is alsoprovided as shown, and prevents the brakes from locking due to thermalexpansion of the brake fluid. The ports 21 and 24 provide borecommunication with the reservoir at different points during the axialtravel of a master piston 25 within the cylinder.

The piston 25 is slideably contained within the bore 14 and is heldtherein by means of a retainer 26 and a snap ring 27. A flange portion28 of the piston divides the bore 14 into a high-pressure chamber 31 anda lowpressure chamber 32 and an axially-spaced, flange portion 33carries a seal member 34 to prevent leakage from the chamber 32 to theambient by way of the open end 17. Piston 25 also includes a taperedrecess 35 which is adapted to receive a force rod 38. The force rod alsocommunicates with an operator-controlled brake pedal (not shown) in aconventional manner.

A piston cup'seal 39 is disposed within the highpressure chamber 31adjacent to piston flange 28. The cup seal is fabricated from awear-resistent, somewhat resilient material, such asPolytetrafluoroethylene, fluorinated ethylenepropylene, or the like, andhas a base portion and a peripheral lip portion'formed integrallytherewith. The cup seal'is provided with a centrallylocated passageway59 and an intersecting contoured counterbore which together transpiercethe cup seal.

A valve, in this case, a poppet valve 40, is provided to selectivelyopen and close the centrally-disposed cup seal passageway. Fixedlyconnected to the valve 40 is a spring retainer member 41. The springretainer engages a spring 45 within the high-pressure chamber 31 andsuch spring exerts oppositely-directed forces against the retainer 41and a check valve 42 to urge the retainer 41, the seal 39, and thepiston 25 toward the open end 17 of the master cylinder while urging thecheck valve 42 toward the outlet end 18.

The check valve 42 allows unrestricted fluid flow therethrough in adirection toward the outlet port on a pumping stroke and blocks flowtherethrough in a reverse direction until such time as fluid graduallyreturn-v ing from the individual wheel cylinders moves the entire checkvalve assembly, under certain conditions,

away from the outlet end and enables the fluid to pass into thehigh-pressure chamber 31.

The spring member retainer 41 is provided with a counterbore 46 and aplurality of transpiercing passages 47 which allow fluid flow throughthe retainer member. Such retainer member is also equipped with acentral bore 48 which is adapted to fixedly engage a stem portion 49 ofthe valve 40 such as by press fitting, staking, or other suitable means.

FIG. 3 in the drawings shows the poppet valve 40 in greater detail. Thevalve is provided with a smalldiameter stem portion 49 and an enlargedportion 52 which includes a plurality of flats 53 and arcuate sections52 forming, with stem portion 49, a plurality of shoulders 56. A headportion 54 of the valve has a contoured surface 55 which is adapted tocoincide with the counterbore 60 of the cup seal 39. With reference toFIGS. 1 and 2, it will be noted that the enlarged portion 52 and theflats 53 penetrate the bore 59 in cup seal 39 and the shoulders 56 abutthe retainer member 41.

As shown in FIG. 2, the components of the present invention provide anunobstructed fluid flow path between the chamber 32 and the chamber 31.Such flow path includes a plurality of ports 61 in the piston flange 28,cup seal counterbore 60 and passageway59, a retainer member counter bore46 and the transpiercing passages 47.

It should be noted that when stroking force is applied to the piston 25by means of the force rod 38 to move the piston 25 rightwardly, to theposition shown in FIG. 1, the poppet valve 40 and the cup seal 39 aremoved, in delayed sequence, towards the outlet end 18 of the pressurechamber 31. When this occurs, the contoured surface 55 of the valve headengages the contoured counterbore 60 in the cup seal and closes off theaforementioned unrestricted flow path. Concurrently with the engagementof the contoured counterbore and the contoured surface of the valvehead, a facing portion of the piston flange 28 makes contact with thebase of the cup seal. Such action completely discontinues communicationbetween the low-pressure chamber 32 and the high-pressure chamber 31.

As the piston 25 moves to the right, cup seal 39 passes the bypass port24 and closes off communication between reservoir 12 and chamber 31.Further movement of the piston 25 toward the outlet end 18 causes thespring 45 to compress and the pressure of fluid in the chamber 31 toincrease. High-pressure fluid from the chamber 31 begins to be forcedout through the port toactivate the individual wheel cylinders of thevehicle. Shortly after. the poppet valve makes closing contact with thecup seal, the cup seal moves axially past the bypass port 24. Thisdiscontinues communication between the high-pressure chamber 31 and thereservoir and causes a rapid increase in pressure in the chamber 31. Atsuch time, the cup seal 39 is forced outwardly by the high fluidpressure into tight sealing engagement with the interior of the mastercylinder.

Upon the discontinuance of force applied by the rod 38, the spring 45immediately begins to force the piston 25, the poppet valve 40, and theretainer 41 leftwardly toward the open end 17 of the master cylinder.This action instantly unseats the poppet valve 40 from sealingengagement with the contoured counterbore 60 and allows pressurizedfluid from chamber 31 to be immediately relieved into the low-pressurechamber 32 through the aforementioned unrestricted flow path. As

the retainer member 41 moves leftwardly toward the open end 17, underthe influence of the spring 45, it will make peripheral contact with thecup seal 39 and will move the seal leftwardly. When this occurs, andwhen the components have all moved to the point where the flange portion33 makes contact with the retainer 26, the assemblage comes to a rest ina static or normal condition such as is shown in FIG. 2.

In the event that the cup seal should move leftwardly at a rate fastenough to cause a reduction in pressure in the chamber 31, make-up fluidfrom chamber 32 can rapidly flow into chamber 31 to increase thepressure therein and avoid a low pressure or cavitation condition. Sucha condition would tend to prevent return of the cup seal 39. Aspreviously stated, such flow occurs through the previously-describedunrestricted flow path.

In FIGS. 4 and 5, an alternate embodiment, essentially identical inprinciple and operation to that just described, but having a slightlydifferent construction, is shown. As shown, a valve 65 is provided inlieu of the previously-described valve 40. The valve 65 has a unitaryflange portion 66 which serves as a retainer member for the spring 45.In lieu of the flats and head portion of the previously-described valve40, the valve 65 is provided with a central passageway 68 and aplurality of small radial bores 69 which communicate the interior andexterior of the valve. The stem portion 67 is received within the bore59 of the cup seal which, in this case, is provided as before with acontoured counterbore 60.

The operation of the master cylinder assembly of FIGS. 4 and 5 isessentially the same as that of the previously-described embodiment.When the assembly is static, as shown in FIG. 5, an unobstructed fluidflow path exists between the chamber 32 and 31 by way of the pistonflange ports 61, the bores 69 and the passageway 68 in the valve 65. Aspressure is applied to force rod 38, the piston 25 is moved rightwardlytoward the outlet end 18 and, since the valve v65 is in contact with thepiston 25, such valve is also moved rightwardly. As the valve 65 movestoward the outlet end of the cylinder, the spring 45 is compressed andthe stem portion 67 moves within the seal bore 59 to discontinue thetransmission of fluids through radial bores 69. Further rightwardmovement of piston 25 causes the piston flange 28 to contact cup seal 39and to move it toward the outlet end 18. When the piston 25 contacts thecup seal 39, a closure is created and the flange ports 61 are blocked,thus fluid is trapped within the chamber 31 except for that which leaksthrough the small bypass port 24. However, additional rightward movementof the piston 25 causes the cup seal to move past the bypass port tocompletely trap the fluid within chamber 31 wherein the pressure thereofis increased. Such pressurized fluid is expelled through the port 20 toactivate the individual wheel cylinders for the vehicle in thepreviously-described manner.

Upon relaxation of the rightward force applied to the piston 25, thespring 45 forces the valve 65 andthe piston 25 leftwardly toward theopen end 17 of the cylinder. This movement will immediately create aflow path between the chamber 31 and 32 by way of the passageway 68 andbores 69 in the valve 65. High pressure in the chamber 31 is therebyrelieved into the lowpressure chamber 32 to equalize the pressures insuch chambers. Further movement of the valve and piston toward the leftwill cause the valve to contact and pick up the cup seal 39 to move itleftwardly. If such leftward movement of the cup seal is rapid enough tocreate a partial vacuum in the chamber 31, then fluid from the chamber32 can flow immediately into the chamber 31 by way of thepreviously-described flow path. Pressure equalization between thechamber 31, 32 will occur, as previously described, whenever the cupseal is separated from the piston 25.

The cup seal valve may obviously take other forms so long as thefunction and performance thereof are in keeping with the principlespreviously discussed. An example of such other valve constructions isshown in FIGS. 6 and 7. The valve 70, like the valve 65, also serves asa retainer member for the spring 45. As did the previously-describedembodiments, the valve 70 provides an unrestricted flow passageway. Thispassageway includes a plurality of equiangularly spaced bores 72 in theretainer portion of the valve and a corresponding plurality of'grooves74 formed along the periphery of the valve stem portion, as shown.

Braking systems incorporating the previouslydescribed master cylindersealing arrangements may be rapidly and efficiently bled. Such bleedingwill cause fluid starvation in chamber 31. At such time, fluid from thereservoir 12 will readily and automatically replenish the needed fluid.by flowing from the chamber 32 to chamber 31 by way of thepreviously-described unrestricted flow paths.

In view of the foregoing, it is readily apparent that the structure ofthe present invention provides an improved master cylinder pistonsealing arrangement which is simple to fabricate and extremelyefficient.

While the invention has been described and shown with particularreference to the preferred embodiments, it will be apparent thatvariations are possible, especially with regard to the particularconstruction of the cup seal valve, and such variations would fallwithin the spirit of the present invention which is not intended to belimited except by the scope of the appended claims.

We claim:

1. In a brake master cylinder having piston means slidably disposedwithin cylinder means, said cylinder means including fluid inlet andoutlet means, a sealing arrangement for said piston means comprising; aresilient cup seal freely movable relative to said piston means and notcarried thereupon disposed within said cylinder means between said fluidoutlet means and said piston means, said resilient cup seal beingtranspierced by centrally-disposed fluid passageway means, valve meansmounted within said fluid passageway means for closing off saidpassageway means when said resilient cup seal is in a firstpredetermined position with respect to said piston means and forpermitting unrestricted fluid flow through said passageway means whensaid resilient cup seal is disposed in a second predetermined positionwith respect to said piston means, first spring means for biasing saidvalve means toward said piston means, a retainer member adapted toengage said first spring means, and said retainer member being fixed toand movable with said valve means.

2. The invention of claim 1 wherein said valve means include a poppetvalve having an enlarged head portion and a stem portion, saidpassageway means including a contoured counterbore seat portion adaptedto engage with respect to said flange said enlarged head portion whensaid resilient cup seal is disposed in said first predeterminedposition.

3. The invention of claim 1 wherein said valve means include a valvehaving a hollow body and a plurality of radial passages communicatingthe interior and exteriorof said body and wherein a portion of saidpassageway means engages and closes off said radial passages when saidresilient cup seal is disposed in saidfirst predetermined position andopens said radial passages when said resilient cup seal is disposed insaid second predetermined position.

4. The invention of claim 1 wherein said valve means include a valvemember having an enlarged portion and an elongated stem portion, saidelongated stem portion being slidably disposed within said passagewaymeans, said enlarged portion having a plurality of arcuately spacedaxial bores therethrough, said stem portion having a plurality ofarcuately spaced axial grooves therein in direct communication with saidaxial bores, and all of said axial grooves being simultaneously closedoff by said piston means when said resilient cup sealis disposed in saidfirst predetermined position.

5. The invention ofclaim 1 wherein said retainer member directly engagessaid resilient cup seal when said resilient cup seal is disposed in saidsecond predetermined position, said retainer member having passage meanstherethrough for permitting said unrestricted fluid flow through saidfluid passageway means when said resilient cup seal is disposed in saidsecond predetermined position.

6. The invention of claim 1 wherein said cylinder means include acylindrical bore formed within a housing member and a fluid supplyreservoir, and wherein first and second port means are provided forcommunicating said bore with said fluid supply reservoir.

7. The invention of claim 6 wherein said first and second port meansinclude respectively a compensating port and a fluid make-up port spacedaxially apart from one'another along said bore and wherein said outletmeans is disposed at one axial end of said bore.

8. The invention of claim 2 wherein said poppet valve is slidablydisposed within said fluid passageway means, and wherein said stemportion is in constant engagement with a portion of said resilient cupseal.

9. The invention of claim 8 wherein said stem portion is provided withflat areas of reduced dimension to permit unrestricted fluid flowthrough said fluidpassageway means past said stern portion disposedtherein.

10. In a brake master cylinder having a main bore with an outlet end, areservoir adjacent to said main bore, a fluid make-up port communicatingsaid bore with said reservoir, a piston having a flange portion slidablydisposed within said main bore between said make-up port and said outletend, passage means transpiercing said flange portion, and biasing meanswithin said main bore for urging said piston toward said makeup port, apiston sealing arrangement comprising; a

flexible free-floating seal member having a passageway therethroughslidably disposed in said main bore adjacent to said flange portion andseparate therefrom, valve means disposed within said passageway andmovable with said seal member and also relative thereto, said valvemeans including retainer means for directly engaging said biasing means,said valve means operative to close said passageway when said sealmember is disposed in a first predetermined position with respect tosaid flange portion and operative to permit fluid flow from saidreservoir through said make-up port and passage means and through saidpassageway when said seal member is disposed in a second predeterminedposition portion. =l

1. In a brake master cylinder having piston means slidably disposedwithin cylinder means, said cylinder means including fluid inlet andoutlet means, a sealing arrangement for said piston means comprising; aresilient cup seal freely movable relative to said piston means and notcarried thereupon disposed within said cylinder means between said fluidoutlet means and said piston means, said resilient cup seal beingtranspierced by centrally-disposed fluid passageway means, valve meansmounted within said fluid passageway means for closing off saidpassageway means when said resilient cup seal is in a firstpredetermined position with respect to said piston means and forpermitting unrestricted fluid flow through said passageway means whensaid resilient cup seal is disposed in a second predetermined positionwith respect to said piston means, first spring means for biasing saidvalve means toward said piston means, a retainer member adapted toengage said first spring means, and said retainer member being fixed toand movable with said valve means.
 2. The invention of claim 1 whereinsaid valve means include a poppet valve having an enlarged head portionand a stem portion, said passageway means including a contouredcounterbore seat portion adapted to engage said enlarged head portionwhen said resilient cup seal is disposed in said first predeterminedposition.
 3. The invention of claim 1 wherein said valve means include avalve having a hollow body and a plurality of radial passagescommunicating the interior and exterior of said body and wherein aportion of said passageway means engages and closes off said radialpassages when said resilient cup seal is disposed in said firstpredetermined position and opens said radial passages when saidresilient cup seal is disposed in said second predetermined position. 4.The invention of claim 1 wherein said valve means include a valve memberhaving an enlarged portion and an elongated stem portion, said elongatedstem portion being slidably disposed within said passageway means, saidenlarged portion having a plurality of arcuately spaced axial borestherethrough, said stem portion having a plurality of arcuately spacedaxial grooves therein in direct communication with said axial bores, andall of said axial grooves being simultaneously closed off by said pistonmeans when said resilient cup seal is disposed in said firstpredetermined position.
 5. The invention of claim 1 wherein saidretainer member directly engages said resilient cup seal when saidresilient cup seal is disposed in said second predetermined position,said retainer member having passage means therethrough for permittingsaid unrestricted fluid flow through said fluid passageway means whensaid resilient cup seal is disposed in said second predeterminedposition.
 6. The invention of claim 1 wherein said cylinder meansinclude a cylindrical bore formed within a housing member and a fluidsupply reservoir, and wherein first and second port means are providedfor communicating said bore with said fluid supply reservoir.
 7. Theinvention of claim 6 wherein said first and second port means includerespectively a compensating port and a fluid make-up port spaced axiallyapart from one another along said bore and whErein said outlet means isdisposed at one axial end of said bore.
 8. The invention of claim 2wherein said poppet valve is slidably disposed within said fluidpassageway means, and wherein said stem portion is in constantengagement with a portion of said resilient cup seal.
 9. The inventionof claim 8 wherein said stem portion is provided with flat areas ofreduced dimension to permit unrestricted fluid flow through said fluidpassageway means past said stem portion disposed therein.
 10. In a brakemaster cylinder having a main bore with an outlet end, a reservoiradjacent to said main bore, a fluid make-up port communicating said borewith said reservoir, a piston having a flange portion slidably disposedwithin said main bore between said make-up port and said outlet end,passage means transpiercing said flange portion, and biasing meanswithin said main bore for urging said piston toward said make-up port, apiston sealing arrangement comprising; a flexible free-floating sealmember having a passageway therethrough slidably disposed in said mainbore adjacent to said flange portion and separate therefrom, valve meansdisposed within said passageway and movable with said seal member andalso relative thereto, said valve means including retainer means fordirectly engaging said biasing means, said valve means operative toclose said passageway when said seal member is disposed in a firstpredetermined position with respect to said flange portion and operativeto permit fluid flow from said reservoir through said make-up port andpassage means and through said passageway when said seal member isdisposed in a second predetermined position with respect to said flangeportion.